Clinical and Economic Impact of Nirsevimab and Bivalent Maternal Vaccine Against RSV Infections in Infants in Italy.

Abstract

This study aimed to estimate the potential clinical and economic impact of nirsevimab and of a maternal vaccine in the prevention of medically attended (MA) RSV-associated lower respiratory tract infections (LRTIs) in the entire cohort of newborns entering their first RSV season in Italy compared with the absence of prevention strategies. A cost-consequence analysis using a static decision tree model previously published was conducted to estimate the RSV-MA-LRTIs and associated mid-long-term complications avoided with each immunization strategy during a single RSV epidemic season. Nirsevimab efficacy was derived from the pooled analysis of Phase 3 MELODY and Phase 2b clinical trials and a protection of 6 months with constant efficacy was considered. For maternal immunization (MI), the efficacy for term infants was derived from MATISSE clinical trial and it was considered until 6 months of age. Zero efficacy was assumed starting from the seventh month for both preventive strategies. The time horizon of the analysis corresponding to one RSV epidemic season. National Health Service (NHS) perspective was considered in the base-case. From the NHS perspective, over the first RSV season, the immunization strategy with MI compared with no preventive strategies could lead to a reduction of 68,358 RSV-MA-LRTIs and 6,417 associated mid-long-term complications. These reductions in terms of RSV‑related health events can be translated into economic savings of about € 24.5 million. The immunization strategy with nirsevimab compared with no preventive strategies could lead to a reduction of 118,123 RSV-MA-LRTIs, 8,480 associated mid-long-term complications. The economic saving associated with these reductions in terms of RSV-related health events was estimated equal to € 34.2 million. Both preventive strategies represent effective measures for the prevention of RSV infections in infants. The organizational impact of these two strategies should also be assessed, in addition to ensuring appropriate counselling for pregnant women and the parents of infants, to avoid missing these immunization opportunities against RSV. These findings may support public health decision-making and inform future policy strategies.